The present invention relates to the field of permanent magnet structures and, more particularly, to permanent magnet structures that produce a working magnetic field that tapers in strength with progression along the magnetic axis.
Permanent magnet structures that produce a working magnetic field are well known in the art. The term xe2x80x9cworking magnetic fieldxe2x80x9d as used herein refers to a magnetic field that is used to do some type of work. A magnetic field used to guide or focus an electron beam is an example of such a working magnetic field.
Some permanent magnet structures are composed of pieces of permanent magnet material arranged to form a shell having an interior cavity. Each piece of permanent magnet material has a magnetization that adds to the overall magnetization of the shell. Depending on the magnetization of the shell, a permanent magnet structure can be designed to produce a magnetic field having a given magnitude along a given axis in the working space located in the cavity of the shell.
Permanent magnet structures may also be designed to provide a working magnetic field having a magnitude or strength that can be mechanically adjusted. Such structures are typically composed of two permanent magnet shells, each producing a working magnetic field in their respective cavities. The shells are arranged such that their internal cavities form a working space within the common internal cavity. Such an arrangement enables the working magnetic fields to interact in the working space to produce, e.g. by vector addition, a composite working magnetic field having a composite magnitude. In addition, the shells are arranged such that they can rotate independent of each other around the concentric axis within the common internal cavity. The ability to rotate permits the user to change the vector relationship between the working magnetic fields produced by each shell. As a result, components of the composite working field in the working space can be adjusted or changed by rotating one shell with respect to the other. For example, U.S. Pat. No. 4,862,128, entitled xe2x80x9cField Adjustable Transverse Flux Source,xe2x80x9d issued to the inventor herein on Aug. 29, 1989, describes obtaining an adjustable working magnetic field by assembling two cylindrical shells, known as xe2x80x9cmagicxe2x80x9d rings or magic cylinders, and rotating the shells to change the magnitude of the working magnetic field in the cavity.
Until now, there has been no available permanent magnet structure to generate an adjustable tapered working magnetic field in the magnetic axis of the working space and common internal cavity of the shells. A tapered working magnetic field is a working magnetic field that changes from a greater magnitude to a lesser magnitude along an axis in the shell cavity. This inventor""s U.S. Pat. No. 5,216,400, entitled xe2x80x9cMagnetic Field Sources For Producing High-Intensity Magnetic Fieldsxe2x80x9d, discloses a magnetic shell formed from either the magic ring or a segmented sphere that produces a tapered working magnetic field along a transverse axis in its internal cavity when the remenance or magnetization of each piece of the shell varies as a function of its polar angle from the axis. However, once that tapered magnetic field is assembled, the working magnetic field generated in its cavity is fixed and non-adjustable. Until now, permanent magnetic structures have not provided a means for varying the taper or the pitch of the taper from a greater magnitude to a lesser one. Thus, there is a long-felt need for a permanent magnetic structure that permits adjusting, varying or fine-tuning the taper of the working field and does not suffer from the disadvantages, limitations and shortcomings of fixed taper magnetic structures.
It is therefore one object of the present invention to provide a device and methods for adjusting a tapered working magnetic field.
It is another object of the present invention to provide a device and methods for adjusting a tapered working magnetic field in permanent magnetic structures.
It is still a further object of the present invention to provide a permanent magnetic structures device composed of magic rings that provides an adjustable tapered working magnetic field, and methods for making same.
To attain these objects and advantages, a permanent magnet structure of the present invention composed of two or more permanent magnet shells is provided, with the first shell being oriented and magnetized to produce a first working magnetic field with a given taper, and a second shell oriented and magnetized to produce a second magnetic field with a given taper that interacts with the first magnetic field. The two magnetic shells are assembled in a way to rotate about a common shared internal cavity and concentric cylindrical axis to form a working space, with the first and second working fields interacting with each other to form a tapered working magnetic field perpendicular to the concentric axis with a given pitch. This structure allows one to adjust or change the magnitude and pitch of the tapered magnetic field along the field axis to advantageously provide a working magnetic field with an adjustable taper.
In particular embodiments, the permanent magnet structures of the present invention comprise at least two permanent magnet shells, with the first shell producing a first working magnetic field with a given taper, and a second shell producing a second magnetic field. Each permanent magnetic shell further comprises a group of magnetic sections that collectively produce a tapered magnetic field. The taper is collective because the assembly of the sections produces the taper. In some embodiments, the magnetic sections are wedge-shaped. The two shells are assembled to share a common internal cavity wherein the first and second working fields interact with each other to form a tapered working magnetic field along the shells"" polar plane in the z direction with a given pitch. The magnetic shells may further comprise a plurality of magnetic shells that all rotate about a common internal cavity. Whenever the first and second magnetic shells rotate around the common internal cavity, this movement or rotation of either shell directly affects the interaction, by geometric addition, of the magnetic fields, and thereby also affects the pitch of the tapered working magnetic field produced in the working space along the magnetic axes and parallel thereto. As a result, one can adjust or change the magnitude and pitch of the tapered magnetic field in the common internal cavity by changing or rotating the relative position of one shell within a set of shells, or rotating one shell with respect to the other, thus advantageously providing a working field with an adjustable taper. One embodiment of this invention provides a variable magic cylinder magnetic structure comprising two or more magic rings. The present invention also encompasses a method for adjusting a tapered magnetic field and a method of adjusting a tapered magnetic field in a magic ring structure.
These and other features of the invention will become more apparent from the Detailed Description when taken with the drawings. The scope of the invention, however, is limited only by the claims.